Converter systems and inverter systems are used throughout electric utility power systems to transfer from and to a utility system grid, respectively. Constant on-time (COT) converter is a converter generally applied in wide-input-voltage-range systems. Generally, COT topology has bad noise immunity and sub-harmonic issue but good transient performance. In addition, the stability of COT topology suffers from limitations on the effective series resistance (ESR) of output capacitors. As a result, an output capacitor with a relatively small ESR may not be suitable for use in a COT converter. Conventionally, there are different ways to improve noise immunity and stability. One of the conventional ways uses inductor current as a compensated ramp for injection to a feedback loop. However, this conventional way needs an extra sample and hold circuit and may increase the complexity of the COT converter.